The present invention relates to an image pickup device and more particularly, to an image pickup device for inputting high-quality color image information for an object to be picked up by using image pickup elements.
In order to obtain color image information, image pickup elements each having sensitivity for a different wavelength such as R, G, and B (Elementary colors) or Y, M, C, and G (Complementary colors) are generally required. For this reason, there have been three types of image pickup systems based on the conventional technology.
Namely, a first image pickup system is based on a technique for obtaining color image information for each color of R, G, and B by incorporating color filters in an optical system for picking up and sequentially switching the color filters. FIG. 35 is a view schematically showing an image pickup device employing the first image pickup system. In the first image pickup system, as shown in FIG. 35, a R (Red) filter 402, a G (Green) filter 403, and a B (Blue) filter 404 are provided as color filters in a section between an optical system for picking-up 401 and an image pickup element 405.
The color filters are sequentially switched to each other by moving the R (Red) filter 402, G (Green) filter 403, and B (Blue) filter 404 in a direction indicated by the arrow S (in the vertical direction in the figure) In the first image pickup system, it takes a long time to obtain color image information due to effects by this switching operation.
A second image pickup system is based on a technique for separating an image of a picked-up object into three colors with a dichroic prism or the like and obtaining color image information for each color from images of the picked-up object each obtained by having been subjected to color separation into R, G, and B respectively with three sheets of image pickup elements, and this technique is generally referred to as a 3CCD system. FIG. 36 is a view schematically showing an image pickup device employing the second image pickup system. In the second image pickup system, as shown in FIG. 36, a dichroic prism 505 is provided in a section surrounded by an optical system for picking-up 501 and a R-image pickup element 502, a G-image pickup element 503, and a B-image pickup element 504.
Although there is a merit of enabling concurrent acquisition of color image information for colors (R, G, and B) in the second image pickup system as compared to that in the first image pickup system, a complicated prism has to be used or three sheets of R, G and B image pickup elements 502, 503 and 504 are required, which causes a price of the device to be extremely high.
A third image pickup system is based on a technique for obtaining color information with sensitivity for a different wavelength for each pixel received by a solid-state image pickup element system. FIG. 37 is a view schematically showing an image pickup device employing the third image pickup system, FIG. 38 is a view showing a color array on a light-sensing element, FIG. 39 is a view showing an example of a picked-up object having light and dark, and FIG. 40 is a view showing a density level corresponding to each color. In the third system, a solid-state color image pickup element 602 has color filters provided on light-sensing elements two-dimensionally arrayed as shown in FIG. 38, and the light-sensing elements are arrayed so that each of the elements has sensitivity for a different wavelength for each pixel.
In this third image pickup system, as shown in FIG. 37, color information can be obtained with sensitivity for a different wavelength for each pixel received by the solid-state color image pickup element 602 through an optical system for picking-up 601. Although there is a merit of enabling acquisition of color image information with a single plate in the third image pickup system, it is not possible to obtain color information for the same section of the same object to be picked up because the light-sensing elements each having sensitivity for a different wavelength are arrayed on one plane.
For this reason, as shown in FIG. 39, when color image information for a certain image of picked-up object having light and dark sections in each pixel is obtained by a solid-state color image pickup element with the color array as shown in FIG. 38, signals corresponding to the colors R, G and B are generated as shown in FIG. 40. The phenomenon described above is generally referred to as a pseudo color. To prevent this type of phenomenon, it is necessary not to receive an image having light and dark sections shown in FIG. 39, namely a high frequency image. Namely, in general, the image is shaded off by providing an optical low-pass filter in the picking-up optical system 601, so that generation of the pseudo color can be prevented by making use of the shading-off.
When the image has been shaded off by the optical low-pass filter, however, a high-resolution image can not be obtained. There has been proposed, as a method of solving this problem, for example, xe2x80x9cImage pickup device for high-quality imagesxe2x80x9d disclosed in Japanese Patent Laid-Open Publication No. HEI 7-322121.
Disclosed in this Publication is a technology in which a position of an image of a picked-up object is displaced to image pickup elements by using a VA (Variable Angle) prism as an optical axis changing device so that a high-quality image is obtained through this displacement. With this technology, assuming a total number of pixels of the image pickup elements is m-pixels obtained by fetching the same image a plurality of times, if images of n-types of different picked-up objects are fetched, images equivalent to nxc3x97m-pixels are obtained.
The technology according to this Publication is a combined system obtained by combining the second image pickup system with the third image pickup system. FIG. 41 and FIG. 42 are views each for explaining this combined system with a color array. In this combined system, color information of C, Y, M and G each for the same section of an object to be picked up is obtained by displacing an image pickup element having the color array (Refer to FIG. 41) of filters for complementary colors of C (Cyan), Y (Yellow), M (Magenta), and G (Green) by one pixel pitch in four directions horizontally and vertically to obtain four sheets of color image information as shown in FIG. 42.
In the image pickup device for high-quality images based on the conventional technology like that disclosed in the Publication, the second image pickup system is performed in time sequence by displacing an image of an object to be picked up, so that four-color image information is sequentially obtained because changing is executed like in the first image pickup system although a pseudo color like in the third image pickup system does not occur. For this reason, although the occurrence of a pseudo color is prevented by the second system, there occur such problems as that an unnecessarily long time is spent for image pickup, that hands are unintentionally moved in taking a picture, or that a two axial displacing device (horizontal direction and vertical direction) is required for displacing an image pickup element in the hour directions horizontally and vertically.
It is an object of the present invention to provide an image pickup device in which occurrence of a pseudo color and unintentional movement of hands in taking a picture can be prevented with a simple configuration.
An image pickup device according to the present invention comprises, an optical input unit for optically inputting an image of an object to be picked up; an image pickup unit, in which light-sensing elements each having sensitivity for a different wavelength are two-dimensionally arrayed, for obtaining color image information from the image of the picked-up object inputted from the optical input unit; a relative position displacing unit connected to the image pickup unit for relatively displacing the image pickup unit and the image of the picked-up object inputted from the optical input unit; and a control unit for driving the relative position displacing unit to obtain a plurality sheets of color image information for the same picked-up object from the image pickup unit and also to obtain color image information for a certain color for one screen according to the plurality sheets of color image information, and further to obtain color image information for one screen using the color image information for the certain color for one screen.
With the image pickup device according to the present invention, the image pickup unit and the image of the picked-up object inputted by the optical input unit are relatively displaced from each other by the relative position displacing unit, and color image information for a certain color for one screen is obtained according to a plurality sheets of color image information for the same picked-up object obtained by the displacement, and further color image information for one screen is obtained according to the color image information for the certain color for one screen, so that, by making use of the fact that the sensitivity for detecting change in color phase is lower than that for detecting change in brightness which is human visual characteristics and a change in hue at a high frequency is not sensed as it is but is sensed as gray, occurrence of a pseudo color or unintentional movement of hands in taking a picture can be prevented with simple configuration.
In an image pickup device according to the present invention, the control unit obtains short color image information for a remarked pixel according to correlation in the certain color.
With the image pickup device according to the present invention, short color image information for a remarked pixel is obtained according to correlation in the certain color, so that short color image information can accurately be computed.
In an image pickup device according to the present invention, the control unit compares color image information for a certain color for the remarked pixel to the color image information for the certain color for other pixels around the remarked pixel, and obtains short color image information for the remarked pixel according to color image information for a pixel around the remarked pixel having the highest correlation.
With the image pickup device according to the present invention, color image information for a certain color for the remarked pixel and the color image information for the certain color for other pixels around the remarked pixel are compared to each other, and short color image information for the remarked pixel is obtained according to color image information for a pixel around the remarked pixel having the highest correlation, so that short color image information can accurately be computed.
In an image pickup device according to the present invention, the light-sensing elements are provided so that, when preparing short color image information for a remarked pixel, at least one available pixel exists around the remarked pixel in each of the horizontal, vertical, and diagonal directions against the remarked pixel.
With the image pickup device according to the present invention, the light-sensing elements are provided so that, when preparing short color image information for a remarked pixel, at least one available pixel exists around the remarked pixel in each of the horizontal, vertical, and diagonal directions against the remarked pixel, so that short color image information can accurately be computed.
In an image pickup device according to the present invention, the control unit compares color image information with a certain color for the remarked pixels to the color image information for a certain color for the available pixels around the remarked pixel, and obtains short color image information for the remarked pixel according to color image information for one of the available pixels around the remarked pixel with the highest correlation.
With the image pickup device according to the present invention, color image information with a certain color for the remarked pixels is compared to the color image information for a certain color for the available pixels around the remarked pixel, and short color image information for the remarked pixel is obtained according to color image information for one of the available pixels around the remarked pixel with the highest correlation, so that short color image information can more accurately be computed.
In an image pickup device according to the present invention, the relative position displacing unit displaces either one of the object to be picked up and the image pickup unit.
With the image pickup device according to the present invention, either one of the object to be picked up and the image pickup unit is displaced, so that displacement occurs in a relative position, and with this feature, it is possible to obtain simple configuration not requiring a plurality of image pickup elements nor a mirror optical system.
In an image pickup device according to the present invention, the image pickup unit comprises a plurality of image pickup elements, and the relative position displacing unit branches an image of an object to be picked up inputted by the optical input unit to a plurality of light paths to have the same image of the object to be picked up as the image of the object to be picked up received by each of the image pickup elements.
With the image pickup device according to the present invention, an image of an object to be picked up inputted by the optical input unit is branched to a plurality of light paths to have the same image of the object to be picked up as the image of the object to be picked up received by each of the image pickup elements, so that it is possible to acquire information for moving video pictures without occurrence of unintentional movement of hands in taking a picture, and also possible to obtain simple configuration not requiring a complicated optical system such as dichroic prism for color separation like a three-plate type of image pickup device.
In an image pickup device according to the present invention, the image pickup unit has filters for three elementary colors of R (Red), G (Green), and B (Blue), and the filters for three elementary colors are arrayed so that the elementary color filter for G (Green), which is the certain color, can be positioned for all pixel positions when displaced by the relative position displacing unit.
With the image pickup device according to the present invention, the filters for three elementary colors of R, G, and B are arrayed so that the elementary color filter for G (Green), which is the certain color, can be positioned for all pixel positions when displaced by the relative position displacing unit, so that the elementary filter of G has wide spectrum sensitivity overlapping both of spectrum sensitivity of R (Red) as well as of B (Blue), and with this feature, an information amount for an image of an object to be picked up increases by acquiring color image information for G over one entire screen, which enables the color image to be matched to human visual characteristics.
In an image pickup device according to the present invention, the image pickup unit has an electronic shutter and a mechanical shutter, sets an effective accumulation time within the each exposure time for the color image information according to a timing for driving the electronic shutter and the mechanical shutter, and finishes a transfer operation by the image pickup unit within the exposure time.
With the image pickup device according to the present invention, an effective accumulation time within the each exposure time for the color image information is set according to a timing for driving the electronic shutter and the mechanical shutter, and a transfer operation by the image pickup unit is finished within the exposure time, so that each interval between accumulation times to obtain a plurality of color image information can be reduced, and with this feature, it is possible to resolve the problems such as unintentional movement of hands in taking a picture.
In an image pickup device according to the present invention, the control unit corrects at least a difference in accumulation times for the plurality of color image information.
With the image pickup device according to the present invention, at least a difference in accumulation times for the plurality of color image information is corrected, so that it is possible to acquire a high-quality image even if there is nonuniformity in exposure when a plurality of color image information is acquired.
Other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.